Reducer Coupling, Slip 10" x 6" (C629-626)

The 10" x 6" PVC Class 125 Reducer Coupling (Slip x Slip) is a large-diameter thermoplastic fitting designed to transition between two significantly different pipe sizes in a straight run — connecting a 10-inch pipe on the large end to a 6-inch pipe on the small end using solvent cement on both slip socket connections. The result is a permanent, concentric, full-bore inline reduction that accommodates a substantial step-down in pipe diameter without elbows, offsets, or additional fittings introduced into the assembly.

The 10" to 6" size reduction represents a meaningful cross-sectional change — the 6-inch downstream pipe carries roughly 36% of the cross-sectional area of the 10-inch upstream pipe, which has direct implications for flow velocity, pressure, and system design at the reduction point. In gravity drainage applications, this transition is typically located where a primary collection main steps down to a smaller conveyance run as the accumulated flow volume decreases along the drainage network. In pressurized systems, the reduction point must be accounted for in hydraulic calculations, as the velocity increase through the reducer affects both downstream pressure and the sizing of any fittings or equipment installed after the transition.

Class 125 PVC fittings are dimensioned to the cast iron pipe fitting pattern — the correct standard for large-diameter drainage, stormwater conveyance, and gravity-flow applications where cast iron fitting geometry is specified or where PVC is being installed as a corrosion-resistant replacement within existing cast iron infrastructure. This dimensional standard differs from Schedule 40 PVC, and the two are not interchangeable at the fitting level in applications governed by cast iron pattern geometry. The concentric geometry of this reducer coupling keeps the pipe centerline aligned through the transition, avoiding the eccentric offset that would require additional support or alignment hardware in a buried or above-ground installation. Manufactured to ASTM D2466 standards and dimensioned to the cast iron pipe fitting pattern for full compatibility with mating Class 125 components in both sizes.

Specifications:

Industries & Applications:

• Municipal Drainage & Stormwater — The core application for large-diameter Class 125 reducer couplings; used in underground stormwater collection networks where a 10-inch primary main steps down to a 6-inch downstream run as branch loads decrease along the drainage system, or where two different-diameter pipe segments must be joined inline at a designed reduction point
• Large Commercial Building Drainage — Specified in below-grade gravity drain mains for large commercial, institutional, and industrial buildings where the primary 10-inch building drain transitions to a 6-inch branch or lateral run serving a lower-load portion of the drainage system
• Civil & Site Utilities — Incorporated in site utility plans for commercial developments, campus infrastructure, and public works projects where underground drainage or stormwater mains transition between standard pipe sizes at engineered reduction points in the collection network
• Industrial Discharge & Process Drainage — Applied in large-bore industrial drain and process discharge systems where a 10-inch collection header steps down to a 6-inch conveyance run serving a lower-volume discharge point or downstream treatment connection
• Cast Iron System Replacement & Retrofit — A direct retrofit fitting for upgrading aging cast iron drainage infrastructure to PVC; Class 125 dimensional compatibility at both the 10-inch and 6-inch ends allows the reducer coupling to be installed at existing cast iron transition points without custom adapters, transition fittings, or dimensional mismatches at either end
• Water & Wastewater Treatment Facilities — Used in gravity drainage, process drain, and effluent conveyance lines within treatment plant infrastructure where 10-inch collection mains transition to 6-inch downstream runs between process areas, treatment stages, or discharge points